1. Field of the Invention
The present invention is related to the field of electrical measurement and network tests, and specifically to the measurement of the resonant frequency of a tuned network and it is also related to the measurement of the "Q" factor of the electrical network.
2. Description of the Prior Art
There is a need to know the resonate frequency of a tuned circuit during adjustment. The prior art used a manually tuned oscillator with an inductor, being suitably exposed and part of the oscillator tuning circuit, coupled directly to the network-under-test by inductive mutual coupling. It is known as a dip meter and as a grid dipper. The oscillator is contained in the tuning head with a calibrated frequency scale. The device of this disclosure is identified as a swept-dip-probe and will display graphically the circuit response. The prior art dip meter device uses an analog meter to indicate resonance. Operation of the dip meter requires a display sensitive to level changes in the r.f. energy absorbed by the network-under-test. The oscillator supplying the r.f. energy is manually tuned over the frequency range of interest. The dip probe uses an r.f. signal generator that is stable and it is automatically swept over the frequency range of interest. The dip probe resonance measurement covers many octaves of the r.f. spectrum in one frequency sweep and displays the response curve of the network-under-test plotted in a graphical form. The dip member uses an integral r.f. source and is subjected to frequency changes due to the degree of coupling. The dip probe r.f. energy oscillator is well isolated from the coupling inductance so that its stability is only slightly affected by the degree of coupling to the network-under-test.
The prior art used indirect voltages and currents as a measurement parameter. They are displayed on analog meter movements. The grid dipper measures grid bias of an vacuum tube oscillator, which is a direct indication of the r.f. voltage level in the oscillator tank circuit. Mutual coupling to a network-under-test reduces the oscillator tank r.f. voltage, dependent on the degree of mutual coupling, and the difference between the r.f. energy frequency and the resonant frequency of the network-under-test. Absorption of the r.f. energy from the oscillator reduces the bias, and the emitter and the collector currents in the solid state oscillator. They are used as indirect resonance indicating parameters.